How come that rocky planets can have moons with atmospheres after millions of years? The moons shouldn't have any magnetic field to protect their atmosphere from the solar wind and could not depend on the magnetic field of the planet alone, as far as I know.

How come that rocky planets can have moons with atmospheres after millions of years? The moons shouldn't have any magnetic field to protect their atmosphere from the solar wind and could not depend on the magnetic field of the planet alone, as far as I know.

Depending on the size, it could take a few billion for an atmosphere to get stripped off, if was large enough. Our moon would have an atmosphere, most likely, if it were larger (in fact it does have one, replenished and stripped away repeatedly, both by the solar wind, just not thick enough to matter, much like Io, so if it were larger its almost certain it'd have one) moons larger than ours (binaries, for example) would almost definitely have an atmosphere, for at least a fraction of the time it's parent planet has one

Living among the stars, I find my way. I grow in strength through knowledge of the space I occupy, until I become the ruler of my own interstellar empire of sorts. Though The world was made for the day, I was made for the night, and thus, the universe itself is within my destiny.

Here is me bothering again. I have installed the latest version of SpaceEngine (0.974 RC2) and I have noticed that some stuff have changed. First of all, there is one location on the pre-saved list titled "These guys have very complex calendar" (RS 8476-1355-7-1350374-381 4.4) which, upon being selected, yields an "Object Not Found" message. In a similar vein, I tried searching for RS 8414-2303-8-8184277-691 but I can't even find stars beginning with RS 8414 on the finder. The old default starting green moon with the gas giant in the back are not on the pre-saved list of locations, do these places still exist within the program? Also, I don't know if it is just a matter of the particular "shuffle result" of procedurally generated planets, but my prior version of SpaceEngine generated a lot of green colored planets (mainly deserts) with atmospheres of Krypton and Xenon as well as pink titans (as well as more exotic ones like dark green ones). However, in this current version, I haven't stumbled with a single planet with a Xenon or Krypton atmosphere while in the previous version I would find them at a ratio of 1 in 30 or 50 planets aproximatelly. Conversely, Terras were relatively uncommon and now they appear quite often. Is this part of the changed or mere randomness from my part?

However, in this current version, I haven't stumbled with a single planet with a Xenon or Krypton atmosphere while in the previous version I would find them at a ratio of 1 in 30 or 50 planets aproximatelly.

That's because in the previous version the atmosphere composition code was more primitive and generated unrealistic atmospheres like that. Now it's been improved a bit so you shouldn't see those anymore. Also those colors weren't realistic either; I implemented them partly as a debug feature to make it obvious when an unrealistic atmosphere had been generated.

Also, your post has nothing to do with this thread, and should have been posted in the Work Progress/Beta Test thread.

That's because in the previous version the atmosphere composition code was more primitive and generated unrealistic atmospheres like that. Now it's been improved a bit so you shouldn't see those anymore. Also those colors weren't realistic either; I implemented them partly as a debug feature to make it obvious when an unrealistic atmosphere had been generated.

Also, your post has nothing to do with this thread, and should have been posted in the Work Progress/Beta Test thread.

Oh, I'm deeply sorry: I just asked here because, so far, whenever I have a doubt of how things worked, it had been answered on this thread. My mistake and thank you for the clarification. I will miss those green worlds but thanks for making things more realistic.

What if you were to shrink Saturn's rings and play them like a Vinyl record? What would it sound like? (It would be my favorite sound)

Added (19.04.2016, 19:34)---------------------------------------------The more I thought about it, the more I realized how much we already know about this circumstance. The gaps in Saturn's rings would just be static in between "songs" and the denser areas of the rings would be louder.

Also, for multiple planets (binary,...) (ex : Pluto-Charon), how to set the system if others who have a mass equivalent to that of the main, we considered them as planets or satellites/moons to it, and how we appointed them (reality and on Space Engine) if it is the case of the planets ?

In addition to the orbit also, I know that on closer you are, the faster we go and there is nothing to stop us (no rubbing) but however, what is strange is that the bodies as even a gravity acceleration towards the center of their parent. How to know if they have a stable orbit, why does the Moon is receding from Earth despite terrestrial gravity (but there is very low) ?

Also, for multiple planets (binary,...) (ex : Pluto-Charon), how to set the system if others who have a mass equivalent to that of the main, we considered them as planets or satellites/moons to it, and how we appointed them (reality and on Space Engine) if it is the case of the planets ?

There isn't an official designation from my understanding, but when the barycenter is outside of the more dominant planet (above the surface) then it is usually considered a binary or double planet. But it is also common to call the smaller of the two a moon. Earth-Luna is sometimes referred to as a double planet system, but I prefer the barycenter rule since it isn't so ambiguous to determine. Earth-Luna have a barycenter inside of the Earth (parent-moon). Pluto-Charon have one outside of Pluto (double planet).

Quotequarior14 ()

In addition to the orbit also, I know that on closer you are, the faster we go and there is nothing to stop us (no rubbing) but however, what is strange is that the bodies as even a gravity acceleration towards the center of their parent. How to know if they have a stable orbit, why does the Moon is receding from Earth despite terrestrial gravity (but there is very low) ?

If there are only two bodies, and no others of significant mass that come close enough then the orbits are going to be very stable. There is an effect called tidal acceleration that tends to trade off rotational energy of the parent body for acceleration of the moon, but the process is very very slow and eventually results in both being tidally locked with each other if the moon orbits slower than the planet rotates (Earth-Luna) or an eventual collision when the planet rotates slower than the moon orbits (Mars-Phobos).

Pluto-Charon are already tidally locked with each other and are therefore stable.

Here is a good illustration showing how the tidal bulge pulls on Luna speeding up Luna's orbit, while Luna tugs on Earth's tidal bulge slowing Earth down. Eventually Luna will be in a much higher orbit and Earth will have slowed down so that they are both tidally locked.

There isn't an official designation from my understanding, but when the barycenter is outside of the more dominant planet (above the surface) then it is usually considered a binary or double planet.

This is a terrible rule, as it depends on the distance between the bodies as much as it does their relative mass. For example, the Sol-Jupiter barycenter is outside of either body. Is it a binary? But the Earth-Moon barycenter is inside Earth, so is it not binary? But in a few billion years, as the Moon moves away from Earth, that barycenter will gradually move outside of Earth. Does that make them suddenly binary while they weren't before? It's silly.

The best way to determine if it's a binary or not is by mass ratio. You need to choose some arbitrary value for this (I prefer 1:20).